| QSPI U-Boot support |
| ------------------ |
| |
| Host processor is connected to serial flash device via qpsi |
| interface. QSPI is a kind of spi module that allows single, |
| dual and quad read access to external spi devices. The module |
| has a memory mapped interface which provide direct interface |
| for accessing data form external spi devices. |
| |
| The one QSPI in the device is primarily intended for fast booting |
| from Quad SPI flash devices. |
| |
| Usecase |
| ------- |
| |
| MLO/u-boot.img will be flashed from SD/MMC to the flash device |
| using serial flash erase and write commands. Then, switch settings |
| will be changed to qspi boot. Then, the ROM code will read MLO |
| from the predefined location in the flash, where it was flashed and |
| execute it after storing it in SDRAM. Then, the MLO will read |
| u-boot.img from flash and execute it from SDRAM. |
| |
| SPI mode |
| ------- |
| SPI mode uses mtd spi framework for transfer and reception of data. |
| Can be used in: |
| 1. Normal mode: use single pin for transfers |
| 2. Dual Mode: use two pins for transfers. |
| 3. Quad mode: use four pin for transfer |
| |
| Memory mapped read mode |
| ----------------------- |
| In this, SPI controller is configured using configuration port and then |
| controler is switched to memory mapped port for data read. |
| |
| Driver |
| ------ |
| drivers/qspi/ti_qspi.c |
| - Newly created file which is responsible for configuring the |
| qspi controller and also for providing the low level api which |
| is responsible for transferring the datas from host controller |
| to flash device and vice versa. |
| |
| Testing |
| ------- |
| A seperated file named README.dra_qspi_test has been created which gives all the |
| details about the commands required to test qspi at U-Boot level. |